Fatigue striation spacing and equivalent initial flaw size in Al 2024-T3 riveted specimens

One of the main concerns of aeronautical structures is structural damage due to fatigue. This phenomenon is accentuated in areas of stress concentration, namely the connection of components. The fuselage is one of the most important structural elements where the connection of the fuselage panels is often done by riveting. Specimens with several geometric configurations are used to study these structures. This work is concerned with the study of one of these specimens, i.e., the lap splice with three rows of rivets and one rivet column. It is part of the IDMEC-Porto contribution to the European project ADMIRE. Stress versus number of cycles results and measurements of fatigue striation spacing along two perpendicular directions using scanning electron microscopy (SEM) are presented. The fractographic reconstitution of fatigue crack growth was carried out. The value of equivalent initial flaw size (EIFS) is calculated using the back extrapolation technique and two models of fatigue crack growth. They consist of a model using the Paris law and another the strain energy density factor concept. The EIFS is used to predict the fatigue behaviour of this structural detail. It is intended to verify the applicability of empirical models based in experimental evidences.